It is known that an SEI (Solid Electrolyte Interface) film (hereinafter referred to as a film) is formed on the surface of a negative electrode active material included in a non-aqueous electrolyte secondary battery. This film is formed mainly due to the reductive decomposition of an electrolyte on a negative electrode at the time of an initial charge and discharge. Once the film is formed, the reaction between the electrolyte and the negative electrode can be suppressed. However, such a film is hardly formed in a non-aqueous electrolyte secondary battery using lithium titanate as a negative electrode active material. This is because a lithium ion absorption/release potential in the negative electrode including a lithium titanate is higher than the negative electrode used in the conventional batteries. When the film formation is insufficient, the reaction between the electrolyte and the negative electrode is not suppressed. In particular, when the battery is stored in a state close to a full charge at a high temperature, the decomposition reaction of the electrolyte is increased. Thus, there is a problem that gas generation due to the decomposition of the electrolyte is increased, resulting in the expansion of the battery. There is also a problem that the capacity retention ratio is decreased due to the rise of the internal resistance.